<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
        }

        .d1{
            width: 400px;
            height: 500px;
            background-color: burlywood;
            margin: auto;
            position: relative;
            background: url(../image/1.jpg) no-repeat 0px 0px / 400px 500px;
        }

        .d2{
            width: 400px;
            height: 500px;
            background-color: rgb(98, 96, 94);
            margin: auto;
            opacity: 0.5;
            position: relative;
            top: -500px;
            visibility: hidden;
        }

        .btn{
            width: 150px;
            height: 30px;
            background-color: rgb(213, 102, 11);
            color: white;
            border: 0px;
            position: absolute;
            bottom: 10px;
            left: 50%;
            margin-left: -75px;
        }

         .d1:hover +.d2{
            visibility: visible;
        }

    </style>
</head>
<body>
    <div class="d1"></div>
    <div class="d2">
        <button class="btn">立即下载</button>
    </div>
</body>
</html>